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प्रश्न
State the periodic law on which Mendeleev's periodic table table was based. Why and how was this periodic law changed?
उत्तर
According to Mendeleev's periodic law, the properties of elements are a periodic function of their atomic masses. This means that when elements are arranged in an increasing order of their atomic masses, the elements with similar properties repeat at regular periods.
However, Henry Moseley, a scientist, showed that the atomic number of an element is a more fundamental property and a better basis to classify elements than the atomic mass. The atomic number increases consistently by 1, from one element to the next, whereas the atomic mass does not change regularly. Also, the atomic number of an element does not change and remains fixed. This led to a change in Mendeleev's periodic law.
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संबंधित प्रश्न
Why do you think the noble gases are placed in a separate group?
An atom has electronic configurations 2, 8, 7.
What is the atomic number of this element?
Describe two anomalies of Mendeleev's periodic classification of elements.
What name were given by Mendeleev to the then undiscovered element germanium?
An element X forms an oxide X2O3. In which group of Mendeleev's periodic table is this element placed?
(a) group II
(b) group III
(c) group V
(d) group VIII
Eka boron : Scandium : : Eka Aluminum : _______
Two elements in the same position : demerit of Newland's octaves : : place for Isotopes : _______
Write scientific reason.
In a group, the size of the atom increases as it goes down from the top.
Which one of the following does not increase while moving down the group of the periodic table?
Match the column:
| Column ‘A’ | Column ‘B’ |
| Alkali metals | (a) Group 18 |
| Halogens | (b) Group 1 |
| Noble gases | (c) Group 17 |
